The present invention relates to an image forming apparatus such as a copying machine of a clamshell type or a printer of a clamshell type.
Image forming apparatuses such as a copying machine and a printer both used for an office work are used extremely frequently, and they are often used by unskilled users. It is therefore desired that those image forming apparatuses are of a structure wherein users can easily cope with daily problems such as paper jamming or the like and can easily conduct simple repair, checking and cleaning for each mechanical portion.
For the purposes mentioned above, there has been proposed an image forming apparatus of a clamshell type wherein a main body of the image forming apparatus is divided into two portions, one is a lower half body in which mechanical units mainly including a sheet conveyance unit or the like are built in, and the other is an upper half body in which mechanical units mainly including an image forming process unit or the like are built in, the upper half body can be opened, when necessary, from the lower half body, and the mechanical units in both the lower and upper half bodies are within easy access and can be handled easily after a front door covering the front side of the main body is opened.
In some image forming apparatuses of a clamshell type such as those stated above, a platen cover and an automatic document feeder are provided so that they may be opened and closed in the direction which is the same as that for opening and closing of an upper half body.
However, in an image forming apparatus wherein a platen cover is provided on an upper half body, when the platen cover on the upper half body is required to be opened from the upper half body while the upper half body is held in its opened position to be away from the lower half body during the course of maintenance, for example, a document, if it is positioned in an document acceptor on the platen cover, may drop or the pages of the document may be turned, which has been a problem.
In an image forming apparatus wherein an automatic document feeder is provided on an upper half body, on the other hand, when the automatic document feeder is required to be opened from the upper half body while the upper half body is held in its opened position to be away from the lower half body during the course of maintenance, for example, there is a possibility that the apparatus inadvertently may be brought down. Granting that the apparatus is not brought down, a document positioned on the automatic document feeder may drop toward the opposite side for the opening direction of the automatic document feeder, or the pages of the document may be turned, which has been a problem.
In view of the situation mentioned above, the present invention has been achieved and its first object is to provide an image forming apparatus wherein a simple structure thereof can prevent a document from dropping, the pages of the document from being turned and the apparatus itself from being brought down.
The present invention relates to an image forming apparatus such as a copying machine or the like, and more particularly, to an image forming apparatus having therein a torque-transmission device employing gears or timing belts.
Image forming apparatuses such as a copying machine and a printer both used for an office work are used extremely frequently, and they are often used by unskilled users. It is therefore desired that those image forming apparatuses are of a structure wherein users can easily cope with daily problems such as paper jamming or the like and can easily conduct simple repair, checking and cleaning for each mechanical portion.
For the purposes mentioned above, there has been proposed an image forming apparatus of a clamshell type wherein a main body of the image forming apparatus is divided into two portions, one is a lower half body in which mechanical units mainly including a sheet conveyance unit or the like are built in, and the other is an upper half body in which mechanical units mainly including an image forming process unit or the like are built in, and the upper half body can be opened, when necessary, from the lower half body. For easier clearance of jammed transfer sheets with opened entire space over a sheet conveyance path, in particular, there is suggested an image forming apparatus of a clamshell and open-in-front type wherein the lower half body and the upper half body can be opened and closed with a supporting shaft running parallel with a sheet conveyance path as a fulcrum.
These image forming apparatuses used by general users in Japan have been required to cope with two zones differing from each other in terms of frequency (50 Hz, 60 Hz) of a power source in Japan. Accordingly, the conventional image forming apparatus has been equipped either with different motor suitable for the zone for installation of the apparatus or with a system wherein members for rotation-transmission are replaced depending on the zone for installation so that the speed of rotation may be adjusted even when the same motor is used in common.
In some image forming apparatuses of a clamshell type, a lower half body and an upper half body are equipped respectively with driving gears and driven gears to be engaged with the driving gears for the purpose of transmitting, for example, a rotary power for a photoreceptor drum provided on the upper half body from a driving motor provided on the lower half body. These gears are required to be disengaged when the upper half body is opened and to be engaged properly when the upper half body is closed.
In some conventional image forming apparatuses of the so-called sidewise-opening type, gears to be engaged with each other for torque-transmission are arranged to be capable of rotating by necessary angle freely, when they are engaged or disengaged, for smooth engagement and disengagement of the gears, as shown in, for example, Japanese Published Application No. 100459/1984. In these image forming apparatuses of the clamshell and sidewise-opening type, a side face of a gear and its moving plane are on the same plane. Therefore, there has been no fear that the side of the tip of the gear hits that of an opponent gear when the apparatus closes, and thereby a recess for interference between tips of both gears, namely a recess in the rotating direction of the gear has been enough.
In the image forming apparatus of the sidewise-opening type, however, a side face of a gear and its moving plane are not on the same plane and tips of both gears approach each other for engagement in the lateral direction when the apparatus closes. Therefore, there have been fears of occurrence of improper engagement caused by an interference between both side surfaces.
Further, it has been a cause for complicating manufacturing processes for an apparatus and also for increasing the production cost thereof that different motors are equipped in advance separately on different apparatuses to cope with two zones differing from each other in terms of power supply frequency. Even in the case of using a common motor for two zones mentioned above, it has been a complicated job for ordinary users to replace accessory members so that the apparatus may cope with each zone.
An object of the invention is to solve the aforementioned problems in an image forming apparatus, and its second object is to provide an image forming apparatus that is free, even in the case of an image forming apparatus of the open-in-front and clamshell type, from a fear of improper engagement caused by mutual interference between the sides of both gear tips.
Another object of the invention is to provide an image forming apparatus equipped with devices capable of being used in common for two different zones in terms of power supply frequency and capable of being selected easily.
However, the lower half body and the upper half body are arranged to be opened or closed with a supporting shaft cutting a sheet conveyance path at right angles as a fulcrum in the image forming apparatus mentioned above. Therefore, an entire sheet conveyance path can not be opened, and clearance of transfer sheet jamming is time-consuming, in particular. In some image forming apparatuses, therefore, the lower half body and the upper half body can be opened and closed with a supporting shaft running parallel with a sheet conveyance path as a fulcrum and a front door covering mechanical units in both the lower half body and the upper half body is provided on the side opposite to the supporting shaft for the lower half body.
Even in the case of the image forming apparatus mentioned above, the upper half body sometimes can not be opened, depending on the position of the supporting shaft for the upper half body to be opened or closed, to the extent necessary for clearing jammed sheets. Further, in some cases, when the upper half body is opened, the upper half body overhangs the lower half body and the necessary floor space of the image forming apparatus increases by the overhung length, which is a problem.
In view of the situation mentioned above, the present invention has been achieved and its third object is to provide an image forming apparatus wherein the portion above the sheet conveyance path can be opened widely and the floor space of the image forming apparatus can be secured easily.
Another transmission device for an image forming apparatus of a clamshell type includes also an example wherein each of a lower half body and an upper half body is equipped with a pulley which is a rotating object and a timing belt that is a rotation-transmitting member is spread over the pulleys.
However, the timing belt is kept being spread over the upper and lower pulleys while the upper half body is being opened. Therefore, there has been a fear that the belt suffers tension caused by the swing of the upper half body. The tension has adversely affected the timing belt and has been a cause for increasing loads of opening and closing actions.
The present invention is intended to solve the problems of an image forming apparatus mentioned and its fourth object is to provide an image forming apparatus wherein tension of a spread driving power transmitting means is lowered during opening and closing actions, resulting in a small load of opening and closing actions.